There is known a technology of searching for corresponding points between a standard image and a reference image obtained by imaging the same object (subject) from different viewpoints by two imaging devices. In this technology, the reference image is searched for a corresponding point at which the same object as that of a reference point of the standard image is captured, based on a degree of correlation obtained by, for example, correlation computations such as sum of absolute difference (SAD) computation and phase-only correlation (POC) computation.
Another process is known in which, for example, a plurality of images having different levels of resolution are generated for each of a standard image and a reference image and are hierarchized per level of resolution, and then, corresponding points are repeatedly searched for through a correlation computation from an upper layer having a low level of resolution toward a lower layer having a high level of resolution in order. This process sets a search area in the next layer based on the parallax obtained in the upper layer having a low level of resolution, and thus can reduce a period of time required for the computation processes up to the lowermost layer having the highest level of resolution.
There is proposed a technology that, in search for a corresponding point of each pixel, determines a layer regarding a level of resolution that is subjected to the process of searching for a corresponding point next in accordance with a degree of reliability, where the degree of reliability is a value indicating a degree of correlation such as SAD value and POC value obtained through correlation computation for the upper layer having a low level of resolution (for example, Japanese Patent Application Laid-Open No. 2009-294733).